The invention relates to a cage segment of a rolling bearing that has two side plates and two connecting pieces that are connected rigidly to each other, wherein the connecting pieces extend parallel to the axis of rotation of the rolling bodies of the rolling bearing and in which the side plates and also the connecting pieces form a pocket for holding a rolling body.
Rolling bearings typically are formed of an inner ring, an outer ring, and multiple rolling bodies arranged between these raceways. To achieve a uniform arrangement of the rolling bodies on the circumference of the rolling bearing necessary for a uniform load distribution and to prevent contact of the rolling bodies with each other, the rolling bodies are usually guided in a bearing cage. For large rolling bearings that are used, e.g., in rolling mills and in wind turbines, the bearing cages are often constructed as bolt cages or as window cages. A bolt cage consists of two closed side rings and multiple bolts arranged between the side rings uniformly on the circumference. A rolling body provided with a central bearing hole is supported so that it can rotate on the bolt. A window cage likewise has two closed side rings and multiple axial connecting pieces arranged between the side rings uniformly on the circumference. The side rings and the axial connecting pieces enclose multiple intermediate spaces usually called windows or pockets, in each of which a rolling body is guided. Depending on the structure and function of the rolling bearing, the rolling bodies can be cylindrical rollers, tapered rollers, or spherical rollers.
Deviating from the closed design, a window cage can also be formed from cage segments that are either connected to each other or are in contact with each other at least in the circumferential direction of the cage. In addition, cage segments are also known that are arranged as separating and guiding elements between the rolling bodies without coming in contact with each other.
From DE 10 2009 016 017 B4, a cage segment reduced to a separating and guiding element in a rolling bearing is known, which has two axially outer, fork-shaped guide bodies with concave thrust surfaces that are connected to each other by a flat axial connecting piece oriented in the radial direction. In the assembled state of the relevant rolling bearing, the cage segments are arranged between two rolling bodies with respect to the circumference and are guided with the base of the guide bodies on the raceway of the inner ring.
In DE 10 2012 223 316 B3, a similar cage segment of a rolling bearing is described that has, in addition to the fork-shaped guide bodies, two side plates partially engaging the two rolling bodies on the end side. The side plates are connected to each other by the axial connecting piece but are not in contact with the side plates of the adjacent cage segments on the circumference. The side plates are used for the lateral guidance of the relevant cage segment by the rolling bodies guided in one of the raceways in side rims and have, on their radial edges, a bulging for the sliding guidance on the raceways of the rings.
In contrast, in DE 10 2011 087 864 A1, a box-shaped cage segment of a rolling bearing is disclosed in which two axial connecting pieces provided with fork-shaped guide bodies are connected to each other by a circumferential connecting piece on the end side. In the assembled state of the relevant rolling bearing, there is a rolling body within the cage segment and two additional rolling bodies on the circumference of the rolling bearing on the outside on one of the axial connecting pieces of the cage segment. In the relevant rolling bearings there are thus rolling bodies guided within a cage segment and rolling bodies guided freely between two cage segments on the end side arranged alternately on the circumference.
For rolling bearings with the specified cage segments, the packing density of the rolling bodies in the rolling bearing is limited by the arrangement of the guide bodies on the axial connecting pieces and is, e.g., less than for corresponding rolling bearings with bolt cages. In addition, such rolling bearings can result in local compacting of rolling bodies and cage segments due to the lack of support of the cage segments in the circumferential direction of the rolling bearing, wherein this compacting can build up and fade away alternately and can lead to increased wear on the contact surfaces between the rolling bodies and the cage segments.
In contrast, from DE 10 2013 207 301 A1 and DE 10 2013 220 833 A1, cage segments of rolling bearings are known, each of which has two side plates that engage the two rolling bodies on the end side approximately half-way and are connected to each other by means of a flat axial connecting piece oriented in the radial direction. On the axial connecting piece of each cage segment there are guide bodies with thrust surfaces for guiding the allocated rolling body. While the cage segment according to DE 10 2013 207 301 A1 has guide fingers arranged on the axial connecting piece and provided with outer sliding bodies for the radial guidance, in the cage segment according to DE 10 2013 220 833 A1, the side plates are provided with radially outer bulges or contact elements. By the arrangement of the thrust bodies on the axial connecting pieces, the circumferential packing density of the rolling bodies is also limited for rolling bearings that are provided with these designs of cage segments. However, because the cage segments are in contact with the adjacent cage segments in the assembled state of the relevant rolling bearing by the end surfaces pointing in the circumferential direction of the rolling bearing, a uniform distribution of the rolling bodies across the circumference is guaranteed for the corresponding rolling bearings.
In contrast, in the not previously published DE 10 2015 200 381 A1, a cage segment similar to the cage segment according to DE 10 2013 220 833 A1 for a rolling bearing is proposed, in which the side plates are connected to each other by two radially staggered round bolts. The axial connecting pieces constructed in this way are used, on one hand, for connecting the two side plates and, on the other hand, for guiding the two allocated rolling bodies. Due to the free intermediate space between the round bolts, a rolling bearing equipped with such cage segments has an increased packing density of the rolling bodies and thus a higher load rating. Due to the relatively large contact surfaces between the round bolts and the rolling bodies, however, an unfavorably high rolling resistance and increased wear can be produced.
In addition, from the not previously published DE 10 2015 206 533 A1, a cage for a rolling bearing according to the class is known that is assembled from a plurality of one pocket segments, wherein each of these one pocket segments holds one rolling body. Such a one pocket segment includes two side plates arranged parallel to each other and two plate-shaped connecting pieces oriented parallel to the longitudinal axis of the respective rolling body, wherein the side plates and the connecting pieces are connected rigidly to each other. On the surfaces of the side plates pointing toward each other there are contact elements for the end-side contacting of the respective rolling bodies and the plate-shaped connecting pieces each have projections that are directed in the circumferential direction of the cage and on which radial thrust surfaces are formed for the respective rolling bodies.
Finally, from the publications DE 10 2009 037 422 A1 and EP 2 264 325 A1, segments each with 4 pockets are known for a segmented rolling bearing cage, from DE 10 26 577 A1, cage segments each with two pockets, and from WO 2012 076 583 A1, cage segments each with one pocket.
For the known segmented rolling bearing cages, it is to be stated that the fewer rolling bodies can be arranged in a cage segment, the larger the number of cage parts that are needed for building a whole rolling bearing cage. This has a disadvantageous effect on the production costs, the bearing support, the transport, and the cage assembly. Indeed, for multi-pocket cage segments, that is, for example, a cage segment with four pockets, this disadvantage is considerably reduced relative to a one pocket cage, therefore with an increasing number of pockets, the tendency of the rolling bodies and the cage segments to become jammed in the rolling bearing increases. It must also be noted that the more pockets a cage segment has, the higher the impact energy is with which such a cage segment filled with rolling bodies can impact a directly adjacent cage segment during operation if a circumferential play is overcome. In this way, the cage wear is comparatively high for cage segments with many pockets. Finally, especially with large rolling bearings, for example, with a diameter of more than 0.5 meters, each cage segment becomes heavier and thus less easy to transport and assemble the more pockets such a cage segment has.